1. Field of the Invention
The invention relates to clamps for surgical procedures and, more specifically, to a clamp assembly especially useful for clamping the ascending aorta during cardiac surgery.
2. Description of the Prior Art
During the course of cardiac surgery in which cardiac function is arrested, it is necessary to isolate the heart and coronary blood vessels from the remainder of the circulatory system. Circulatory isolation of the heart and coronary blood vessels is usually accomplished by placing a mechanical cross clamp externally on the ascending aorta downstream of the ostia of the coronary arteries, but upstream of the brachiocephalic artery so that oxygenated blood from the cardiopulmonary bypass system reaches the arms, neck, head, and remainder of the body. Using conventional techniques, the sternum is cut longitudinally (a median sternotomy) thereby providing access between opposing halves of the anterior portion of the rib cage to the heart and other thoracic vessels and organs. Alternatively, a lateral thoracotomy is formed, wherein a large incision is made between two ribs and the ribs are retracted. A portion of one or more ribs may be permanently removed to optimize access.
Regardless of whether a sternotomy or a thoracotomy is performed (both collectively referred to herein as a xe2x80x9cgross thoracotomyxe2x80x9d), the opening in the chest wall must be large enough to permit a cross clamp to be placed externally on the ascending aorta, thereby isolating the heart and coronary arteries from the remainder of the arterial system. A problem with existing cross clamps is their excessive size. A cross clamp usually includes a clamping portion from which integral actuating handles project. The clamp occupies a relatively large portion of the operative site, thereby requiring that the sternum or ribs be retracted to a greater extent than is desired. This is a significant factor in open-chest surgery, because the trauma caused by creating large openings in the chest wall often entails weeks of hospitalization and months of recuperation time.
Recently, techniques have been developed to facilitate the performance of cardiac procedures such as heart valve repair and replacement, coronary artery bypass grafting, and the like, using minimally invasive techniques that eliminate the need for a gross thoracotomy. Coronary artery bypass grafting, heart valve repair and replacement, and other procedures can be performed through small incisions or cannulae positioned in the chest wall. In one recently developed technique, a clamp is introduced into the patient""s thoracic cavity through a percutaneous intercostal penetration in the patient""s chest, typically using a trocar sleeve. The clamp is detachably mounted to the distal end of a clamp positioner. After the clamp is positioned around the ascending aorta, the clamp is actuated from outside the patient""s thoracic cavity to squeeze the aorta and partially or completely block fluid flow therethrough. The clamp then is disengaged from the distal end of the clamp positioner and the clamp positioner is removed from the thoracic cavity to provide enhanced access to the region in question.
Although the referenced device permits cardiac surgery to be conducted with significantly smaller openings formed in the chest wall, there is a concern about the reliability of the clamp and whether a connection can be reestablished between the clamp and the clamp positioner when it is necessary to remove the clamp. A failure of the clamp or the inability to remove the clamp could have disastrous consequences for the patient.
Despite the advantages of minimally invasive cardiac surgery, certain situations still call for the use of a gross thoracotomy. In such circumstances, there remains a need for an aorta cross clamp that is smaller than existing cross clamps but which is extremely reliable and easy to use. In those cases where minimally invasive surgery is indicated, there is a need for an aorta cross clamp that is easy to apply to the ascending aorta, which is reliable in use, and which can be removed without fail.
In response to the foregoing concerns, the present invention provides a new and improved aorta cross clamp assembly. In one embodiment especially suited for use during a gross thoracotomy, a clamp having movable jaws is provided with a removable actuator having movable handles. Initially, the actuator is connected to the clamp with the jaws in an open position. When the actuator handles are closed, the jaws also will be closed. The clamp is provided with a toothed retainer that prevents the jaws from being opened accidently. The actuator can be detached from the clamp and removed from the operative site, leaving the locked clamp in place. When it is desired to remove the clamp, the actuator can be reattached to the clamp and used to disengage the toothed retainer. The actuator then can be used to spread the jaws in order to permit the clamp to be removed.
The clamp and the actuator are provided in two forms. In one form, the toothed retainer is engaged and disengaged by movement toward and away from the jaws (xe2x80x9chorizontalxe2x80x9d movement). In the other form, the toothed retainer is engaged and disengaged by movement generally perpendicular to the jaws (xe2x80x9cverticalxe2x80x9d movement).
In another embodiment especially suited for use during a minimally invasive surgical procedure, a clamp having movable jaws is provided with a slender, flexible, actuator that is not intended to be removed during use. The actuator has a proximal end that defines a handle and a distal end that is connected to the clamp. The jaws are actuated by axial movement of a screw that is connected to the end of a cable included as part of the actuator. The screw passes through a slotted nut that permits non-rotational axial movement of the screw in one direction, but which requires that the screw be rotated in order to move in the opposite direction. A stem having a knob is attached to the proximal end of the cable and extends outwardly from the handle.
When the knob is pushed inwardly (toward the handle), the stem and the cable are advanced, thereby axially moving the screw and closing the jaws of the clamp. The nut prevents the jaws from being opened inadvertently. When is it necessary to remove the clamp, the knob is rotated. This causes the stem, cable, and screw to be rotated. When the screw is rotated, it is moved axially relative to the nut and pulls the jaws to the open position.
The present invention provides an aorta cross clamp that can be used for cardiac surgery during either a gross thoracotomy or a minimally invasive procedure such as a percutaneous intercostal penetration. With any embodiment of the invention, the clamp assembly is compact, reliable, and easy to apply and remove. The foregoing and other features and advantages of the invention will be apparent from an examination of the specification and claims that follow, including the accompanying drawings.